Beginning in December 2013, new tables and maps in the Electric Power Monthly provide detailed accounting of generator additions and retirements, as well as their effects on total capacity by fuel and technology type, on a state-by-state basis.

The state-level detail in the tables can be represented using maps like the one above. Maps make it easier to see, for example, the concentration of new solar generators in the Southwest, natural gas generators in Texas and along the Atlantic Coast, and wind generators in the Plains region that are expected to come online between December 2013 and November 2014.

Power plant owners and operators report plans to modify or retire existing generators, or build new generators, every year as part of EIA's Annual Electric Generator Report. A monthly survey prompts respondents for updates to plans for new builds, modifications, or retirements during the 12 months leading up to the expected change. EIA also follows trade press announcements and third-party tracking services to identify potential planned generators to include in the data collection process.

All generators at plants with at least one megawatt of capacity are represented in these surveys, including most large industrial and commercial generators. Smaller installations, such as residential rooftop solar, are not represented; instead, data for such installations are typically reflected in aggregate reporting from electric utilities that track the interconnection of these distributed systems to their distribution networks.